Abstract: A ferromagnetic metal thin film recording medium having a nonmagnetic substrate, a ferromagnetic metal thin film formed on the nonmagnetic substrate, a dry etched layer which is formed in a surface layer of the ferromagnetic metal thin film and contains oxygen atoms in a higher concentration than the remaining part of the ferromagnetic metal thin film, a hard carbonaceous film formed on the dry etched layer of the ferromagnetic metal thin film, a lubricant layer formed on said hard carbonaceous film, and optionally a modified layer which is formed on the hard carbonaceous film and has a thickness of less than 3 nm, and comprises carbon, nitrogen and oxygen atoms with an atomic ratio of nitrogen to carbon being at least 0.8%, which recording medium has improved running stability, durability and weatherability while maintaining electromagnetic conversion characteristics.

Abstract: A magnetic recording medium produced by treating a magnetic recording medium which comprises a non-magnetic substrate and a magnetic layer formed on said substrate in an atmosphere kept at a temperature of at least 50.degree. C., with applying a tension of 1 gf. or less per 10 mm width to said magnetic recording medium in a treating time which is in a range on or above a line having a slope of at least 5000 in terms of .DELTA.ln(L)/.DELTA.(1/T) and passing a point of 0.5 second at 100.degree. C., when ln(L) is Arrhenius plotted against an inverse of an absolute temperature T (1/T), which medium has suppressed change of magnetic properties with time and improved corrosion resistance.

Abstract: A ferromagnetic metal thin film recording medium having a nonmagnetic substrate, a ferromagnetic metal thin film formed on the nonmagnetic substrate, a dry etched layer which is formed in a surface layer of the ferromagnetic metal thin film and contains oxygen atoms in a higher concentration than the remaining part of the ferromagnetic metal thin film, a hard carbonaceous film formed on the dry etched layer of the ferromagnetic metal thin film, a lubricant layer formed on said hard carbonaceous film, and optionally a modified layer which is formed on the hard carbonaceous film and has a thickness of less than 3 nm, and comprises carbon, nitrogen and oxygen atoms with an atomic ratio of nitrogen to carbon being at least 0.8%, which recording medium has improved running stability, durability and weatherability while maintaining electromagnetic conversion characteristics.

Abstract: A fluorine containing diester of an alkyl- or alkenylsuccinic acid having the general formula: ##STR1## wherein R.sub.1 represents an alkyl or alkenyl group, at least one of R.sub.2 and R.sub.3 is a fluoroalkyl or fluoroalkenyl group, the remaining of R.sub.2 and R.sub.3 is an alkyl or alkenyl group, k, l, m and n are 0 or an integer not less than 1, respectively, and k+l are an integer of not less than 2, which provides an excellent lubricating property under any environment from low humidity to high humidity, and is particularly suitable for use in a magnetic recording medium.

Abstract: A magnetic recording medium comprising a back coating layer formed on a surface reverse to a magnetic layer and a carbonaceous film which is formed on the back coating layer and contains fluorine atoms and silicon atoms and/or nitrogen atoms and in which a concentration of fluorine atoms decreases in a depth direction from a surface of the carbonaceous film, while a concentration of the silicon and/or nitrogen atoms increases in the depth direction from the surface of the carbonaceous film, which recording medium has improved running stability, durability and weatherability while electromagnetic conversion characteristics are maintained.

Abstract: A magnetic recording medium comprising a non-magnetic substrate, a ferromagnetic metal film formed on said non-magnetic substrate, a carbon film which is formed on said ferromagnetic metal film and in which a concentration of at least one element selected from the group consisting of silicon, phosphorus, sulfur, tin and indium is or concentrations of boron and at least one element selected from the group consisting of tin and indium are decreased in a depth direction from the surface of said carbon film, and a lubricant layer formed on said carbon film, which medium has improved running durability and corrosion resistance.